Per Shifts

#include <bits/stdc++.h>

using namespace std;

#define MAX 100000
#define mod 1000000007

long long store[MAX + 5];

void fill_store (void) {
    long long i; store[0] = 1;
    for (i = 1; i <= MAX; i++) store[i] = (i * (store[i - 1] % mod)) % mod;
}

int parity (long long perm[], int len) {
    int check[len + 5], j; int cycle = 1;
    memset(check, 0, sizeof check); int res = 0;
    for (j = 1; j <= len; j++) {
        if (check[j] == 0) {
        check[j] = 1; cycle++; int k = j;
        while (check[perm[k]] == 0) {
        check[perm[k]] = 1;
        k = perm[k];
        cycle++;
        }
        res += (cycle % 2);
        cycle = 1;
    }
    }
    return res % 2;
}

// incomplete
long long index (long long perm[], int len) {
    long long res = 0;
    for (int j = 1; j <= len; j++)
        res += (((perm[j] - 1) * store[len - j]) % mod);
    return res % mod;
}

bool is_circ (long long A[], long long B[], int len) {
    long long AA[len + len + 5], k, one;
    for (k = 1; k <= len; k++) {
        AA[k] = A[k]; AA[len + k] = A[k];
        if (A[k] == 1) one = k;
    }
    bool res = true;
    for (k = one; k < one + len; k++) {
        if (AA[k] != B[k]) {
            res = false;
            break;
        }
    }
    return res;
}

int main() {
    fill_store();
    int i, T, N, K; long long P[MAX + 5], Q[MAX + 5];
    scanf("%d", &T); while (T--) {
        scanf("%d %d", &N, &K); bool flag = true;
        for (i = 1; i <= N; i++) scanf("%lld", P + i);
        for (i = 1; i <= N; i++) {
            scanf("%lld", Q + i);
            if (flag && Q[i] != P[i]) flag = false;
        }
        int parP = parity(P, N), parQ = parity(Q, N);
        long long lex = index(Q, N);
        if (K == 1) printf("%lld\n", flag ? lex : -1);
        else if (K == N) printf("%lld\n", is_circ(P, Q, N) ? Q[1] : -1);
        else if (K % 2) printf("%lld\n", parP == parQ ? lex/2 : -1);
        else printf("%lld\n", lex);
    }
    return 0;
}